Observation: Silver Fork

Observation Date

2/28/2014

Observer Name

Kobernik/Kendall/Gagne

Region

Salt Lake » Big Cottonwood Canyon » Silver Fork

Location Name or Route

Silver & Days Forks

Weather

Sky

Overcast

Precipitation

Light Snowfall

Wind Direction

Southwest

Wind Speed

Moderate

Weather Comments

Temps stayed below freezing, but felt warm in the am until the sky turned overcast by early afternoon. Winds were Moderate out of the SW, with stronger gusts along the upper elevation ridgelines. Light snowfall when exiting late afternoon.

Snow Characteristics

New Snow Depth

12"

New Snow Density

Medium

Snow Surface Conditions

Powder

Wind Crust

Melt-Freeze Crust

Damp

Snow Characteristics Comments

About 25-30 cms (10-12") storm snow with an easy-to-find density inversion just above the old snow surface. Some 4F winds drifts up to about 30 cms along the leeward ridges from SW winds, although we were also finding some cross loading along terrain features. East and South aspects were crusted by early afternoon, but North aspects still had soft snow at the surface. Didn't look at much West-facing terrain in the afternoon, but am guessing with increasing cloud cover, wind, and cooler temps, West aspects may not be crusted.

Red Flags

Recent Avalanches

Wind Loading

Cracking

Red Flags Comments

Widespread wind loading mostly along ridge lines with fresh wind drifts that were sensitive to ski cuts. Saw several small soft-slab avalanches release along north-facing Silver Fork headwall in the early afternoon. These seemed to be triggered by wind-loading and occurred during a spike in winds about mid-day.

Avalanche Problem #1

Problem

Persistent Weak Layer

Trend

Increasing Danger

Problem #1 Comments

The most reactive snow we were finding today were fresh wind drifts in mid and upper elevations from the Southwest winds. These were mostly on North through East aspects, although some cross-loading was occurring as well around terrain features. These were failing in a density inversion just above the old snow surface, and were mostly 20-40 cms thick (8-16") 4F-hardness. These were not wide propagations, and they seemed to need a steeper slope (35 degrees or steeper) to become reactive.

Comments

Travel today was through Silver Fork and exiting Days Fork. Quite apparent there was a density inversion down about 25-30 cms (10-12") just above the old snow surface. We were able to ski cut a few soft slabs on steeper aspects, and for the most part we were only able to get failures in this density inversion on wind-drifted slopes. Hazard today was "Manageable Considerable" - we saw natural avalanches and ski cutting did produce small soft slabs running within the new snow. Well-placed ski cuts along ridgelines and steeper rollovers were quite effective at managing and mitigating today's hazard. Saturday's hazard depends upon how much water weight and wind-loading occurs in the expected storm. Larger water amounts and stronger winds will likely make Saturday's hazard "Unmanageable" and either Considerable or High.

Narrative: Gagne Photos-Video: Kobernik

Video